THE TEETH 229 



when teeth show weakness and seem not to be well 

 nourished, rubbing the gums a few times a day will 

 often improve the circulation and result in general 

 benefit. 



But surely it is not necessary to bother about keep- 

 ing the milk teeth clean, when, at the most ; they serve 

 such a short period ! This is a mistaken idea which 

 many people have. The milk teeth should be kept 

 clean from the beginning. They should also be fre- 

 quently examined by a dentist, and any cavities 

 promptly filled. What a waste of time and money 

 such care seems to be ! Not so, when we consider the 

 damage that may follow if they are allowed to decay 

 or are removed too early. The upper central incisors 

 usually come into a baby's mouth about the fifth or 

 sixth month. The other milk teeth keep coming 

 gradually, the second molars, which appear from the 

 twenty-first to the thirty-sixth month, being the last. 

 The first of the permanent set, the sixth-year molars, 

 appear, as a rule, about the sixth year. They usually 

 come before any of the milk teeth are lost, and, for 

 this reason, are often thought to be temporary. How- 

 ever, if the number counted in either jaw is more than 

 ten, one may be sure the new arrival is a permanent 

 tooth. 



The incisors, bicuspids, canines, and second molars 

 of the permanent set come in from the seventh to the 

 thirteenth years. As all the permanent teeth come 

 in, the roots of the first teeth are gradually absorbed 



